Circuit arrangement for recording telephonic communications



Feb. 21, 1939. R. MILDE 2,147,820

CIRCUIT ARRAN GEMENT FOR RECORDING TELEPHONIC COMMUNICATIONS Filed March 12, 1955 Patented Feb. 21, 1939 omcorr ARRANGEMENT F032. RECORDING TELEPHONIC COMMUNICATIONS Rudolf Milde, Berlin-lankwitz, Germany, assignor to C. Lorenz Aktlengesellschalt, Berlin-Tam,

pelhoi', Germany Application March 12,

1935, Serial No. 10,618

In Germany January 15, 1935 7 Claims.

It is well known, to record telephonic communications by means of electromagnetic talking machines which receive the communications whenever the subscriber is absent. It is known also to use machines of this kind for recording intercommunications carried on between telephone stations, such machines then being con nected in parallel therewith. The invention relates to arrangements intended for the first-said pm'pose.

The invention is described hereafter by way of example, reference being had to the accompanying drawing in which Fig. l is a diagrammatic representation of the whole arrangement, Fig. 2 a diagrammatic detail view showing a modification.

In Fig. 1, a subscriber's station is designated I. Connected to the subscribers lines 2, 3 is a relay d by which either the station I or the electromagnetic recording arrangement is attached. A condenser 5 is connected in parallel with relay t. The connection takes place over condensers t, l. Relay 4 is tuned to the call frequency which otherwise will actuate the ringer of the called subscriber's station. 'In this way, on the arrival of the call signal the station I becomes disconnected, while the electromagnetic talking machine becomes connected. This relay must eflect the same condition of connections as is otherwise broughtabout by taking oil the receiver.

Relay 4 need not be constructed in the simple manner described above. In fact, it is advantageous to arrange that the electromagnetic talking machine shall become connected only after some time, for instance after the call signal has arrived three times. This has the advantage that the electromagnetic talking machine shall only be connected if the subscriber is absent. It is, however, possible also to provide a switch by means of which the subscriber should keep the relay disconnected as long as he may be within thereach of the telephone. When leaving the vicinity he has to reconnect the relay. Such method, however, has the disadvantage that this switching is easy to forget. It is therefore advantageous to construct the connecting device in the manner described above, namely so that switching over shall only occur after a certain number of call signals have arrived. This may be performed by means of the well-known stepping switches, for example. I

Relay! is provided with a locking or holding coil or the like (not shown), in order that the connections eflected by it be maintained until has become energized then the lines 2, 3 are through contacts 8, 9 in connection with the recordingdevice. in denotes a timing relay, such as a stepping switch by which a device is cut in that indicates who is connected.

In the case represented, a simple electromagnetic sound reproducing machine is provided for this purpose. This has an endless record carrier ll which is driven by a motor E2. The motor it not only serves to drive the arrangement that states which subscriber is connected but may drive also the device by which an incoming communication is recorded, 1. e. a communication for station l. Motor i2 is started by a contact it, likewise actuated by relay' l. A battery it serves to feed the motor. On the record carrler it either the subscribers call number, that is the number of station l, or his name is recorded. Also brief communications may be recorded here, for example that the subscriber is not at home but that the recording device is ready for receipt. Ii merely the subscriber's call number or name is recorded, then it is advantageous to repeat this record, since experience has shown that the first announcement is not in any case clearly understood. It may be advantageous that the subscriber himself produce the record for the said first announcement, in order that the calling subscriber may be able also to know him by the idiom of speech.

It is possible also to employ instead of the recording body H another suitable device. For instance, it may be intended to indicate the subscribers number by sounding dots or by Morse signals.

l The record on the body II is in a well-known manner derived by the talking head l5. After the reproduction of this record has been finished, relay l0 disconnects the'lines 2, 3 from the talking head l5 and connects them through to the device ll intended for recording incoming communications. Included in the wires attached to this device is a, switch 16. The talking head of the device ll is designated I8. When communications are being recorded, the switch It occupics its left hand position as viewed in Fig. 1.

For enabling these records to be heard by the subscriber of station I, the switch l6 must be set to the right in Fig. 1, whereby a pair of head phones I9 is included. The recording body I! must be respooled for such reproducing, as is usual with machines of this kind.

The arrangement as thus far described is completed by an additional device. On the shaft of the motor l2 a small phonic wheel 20 is fixed. The magnet coacting therewith is denoted by 2|. By the rotation of this toothed wheel 20 an alternating current of a moderately high periodicity is generated.

Such alternating current is transmitted to the lines 2, 3 in order that the calling subscriber may be able to ascertain whether the recording device is still running. It is noteworthy in connection with this feature that it has proved unpleasant to the calling subscriber if the recording device is simply connected without enabling him to hear in a sense the breathing of the called subscriber.

If the amplitude is kept low enough a checking tone such as that produced by the arrangement 20, 21 may be recorded too to form a sort of primary sound on reproduction. Should it not be desired to record this tone, then a filter 22 is inserted by which the tone is prevented from acting on the recording device l1. The frequency of this tone is preferably within a range which is of inferior importance to the understanding of the recorded communication. The well-known circuits of the high and low frequency art may be arranged here to form the filter 22. In the simplest case a series-resonant circuit, comprised of a series combination of inductance and capacity and connected in parallel with lines 2, 3, will be suflicient.

The checking tone may however form the record of a contrivance similar to the device II, in order to be reproduced in the manner customary inthese devices.

The transmission of this tone is preferably made to depend upon the several parts of the ar-. rangements being ready for operation. This may be ensured by a closed-current connection. Supervisory arrangements of this kind are wellknown, so that they need not be explained here more fully.

It is not necessary to produce the checking tone continuously, but it may be given intermittently, for instance every 20 seconds. This de-, pends upon the requirements involved in the respective mode of service.

The checking tone given during the recording may be produced by the same arrangement as is used for advising the calling subscriber that the called subscriber is absent, that however the recording device is ready for operation. The arrangement in this case may be such that by the phonic wheel-20 a tone is generated which after the call has been effected is transmitted to the lines without being amplified, which however is weakened as soon as the recording device is connected. To such end there may be included in the circuit of the phonic wheel a resistance which is first short-circuited, the short-circuit then being with respect to the recording device.

interrupted. The device H is in this way dispensed with. v

The superposition of the checking tone may be effected also with the aid of a transformer connected for instance in the manner shown in Fig. 2. The coils 23, 24, 25 are so connected and coupled that the ehecking tone shall annul itself When the recording is finished relay 4 becomes deen'ergized, as the locking circuit thereof is interrupted, and the system is restored into its normal state, that is, station I is again attached to lines 2, land the motor 12 is stopped. For hearing the reproduction of the record, the switch It is set to the right as stated already, and moreover a switch 28 is closed so as to start the motor,

contact l3 being bridged over by the switch 26. There must of course be provided also means, customary in machines of this kind, for changing the direction of rotation, in order to recoil the record body and then to hear the reproduction. These means need however not be described here more fully since they are well-known with such machines.

Instead of the timing relay l and the other relays provided in the circuit arrangement, sets of contact springs may be disposed which are actuated by a cam cylinder, for example in such a manner that this cylinder is coupled by a gearing with the shaft of the motor in order to effect the requisite switching operations in due succession. Such gearing is preferably given an adjustable gear ratio in order that the arrangement be usable for different recording times. This may for instance be attained in such a manner that the subscriber is by means of different gearings enabled to select recording times of 1, 2, 3 minutes, and so on. In the latter case it will be necessary to combine with the said announcement, which states to the calling subscriber that the called subscriber is absent and that as a remedy the recording device is ready to receive, an information as to how long this device will be ready. This is easy to effect by means of suitable signals.

The recording device need not be driven directly by the shaft of the motor l2 as shown in the drawing, but the telephone-supervising machines or dictating machines usual nowadays may be employed, the said cam cylinder at the same time effecting the connection of the machine. Such machines are in general provided with a so-called controlling station located at the place where the telephoning or dictating person is occupied, while the recording body proper, viz., a steel wire or tape, with the talking head and driving mechanism constitutes a separate contrivance disposed at another place. Connected in parallel with this controlling station may be a switching arrangement which is actuated by the said cam cylinder and acts to insert the recording device inclusive of amplifying means and the like. This has the advantage that the machines usual nowadays may be employed directly.

The invention is not limited to the application of recording devices which operate by means of recording steel bodies but may be employed in the same manner with other recording arrangements, such for instance as those whose sound record carriers are plate-shaped, the record being cut into the plate, or those with which the record is marked on the record carrier in the manner known from sound films.

What is claimed is:

1. In a system for recording speech, a recorder, a telephone line, means coupling the telephone line to the recorder during the period of speech recording, means for impressing a continuous tone signal outside of range of essential speech frequencies on said telephone line throughout the same period, and means for preventing interference of said continuous tone signal with the voice signals being recorded.

2. In a circuit arrangement for purposes of recording telephone communications, a telephone line, a recorder, means for coupling the recorder to the line for recording of speech, means for transmitting an acoustical signal over the line while said recorder is so coupled to the line and further means comprising a series resonant by- 7:

a,141,s'ao

pass filter circuit for suppressing the transmis- I to the line for recording of speech, means for transmitting an acoustical signal over the line while said recorder is so coupled to the line and further means comprising mutually opposing transformer winding for suppressing the transmission-oi said signal to said recorder.

4. In a circuit arrangement for purposes of recording speech communications, a transmission line coupled by transformer means to a recording apparatus, signaling means, and connections forming a network whereby said signaling means is coupled to said line for transmission of a continuous audible signal'thereto during recording, while said signaling means and said recorder constitute substantially conjugate branches oi the resulting network.

5. Ina system for recording speech, a tele- 'phone line, a recorder, a continuous tone gen,-

erator for generating a tone outside the range of essential speech frequencies, means for establishing a connection between said telephone line and said recorder for recordingfspeech transmitted over said line, a coupling means between said tone generator for applying to said line a continuous tone signal throughout the period of connection, and means for preventing said continuous tone signal from being transmitted to i said recorder.

8. In a circuit arrangement for the purpose of recording a telephone communication transmitted from a calling subscriber station to a called subscriber station, .a recorder at said called station tor recording the communication transmitted from said calling station, means for transmitting a continuous tone signal from said called station to said calling station throughout the period of recording and further means at said called station to block said tone signal from said recorder, whereby said calling subscriber is continuously apprised of connection with said called subscriber station.

7. In a circuit arrangement for the purpose of recording a telephone communication transmitted from a calling subscriber station to a called subscriber station, a recorder at said called station for recording the communication transmitted from said calling station, means for transmitting a continuous tone signal from said called station to said calling station throughout the period of recording, and filter means at said called station to block said tone signal from said recorder, whereby said calling subscriber is continuously apprised of connection with said called subscriber station.

RUDOLF MILDE. 

